79 research outputs found
Environmental Influences on the Evaporation Rate of Horticultural Disinfestants
No full textThe evaporation rate of disinfestants when sprayed on production surfaces is expected to vary under different weather conditions, but it is unknown how that affects efficacy. This study was an initial investigation into how the evaporation rates of water and six commercial disinfestants vary under eight weather condition categories. Additionally, an empirical model was developed on the evaporation rate of water in response to air temperature, relative humidity, solar radiation, vapor pressure deficit, and wind speed under the same eight weather condition categories. Isopropyl alcohol lost more weight due to evaporation over 4 h (P < 0.0001) than all other disinfestant solutions, and no differences (P = 0.05) existed between the other five disinfestant solutions and water. Isopropyl alcohol had a mean percentage weight loss of 71% under hot and sunny conditions, 43% under cool and cloudy conditions, and 6% under indoor laboratory conditions. Water, hypochlorite, quaternary ammonium, and peroxy disinfestant solutions evaporated at a similar rate over 4 h, with an approximate mean percentage weight loss of 17% under hot and sunny conditions, 6% under cool and cloudy conditions, and 1% under indoor laboratory conditions. The regression model that best explained the influence of weather on evaporation included the variables solar radiation, temperature, and wind speed (P < 0.0001, R2 = 0.5603). This information will be used further to model the evaporative rate of disinfestants under the same range of weather conditions when applied to multiple types of substrate materials that represent common horticultural plant production surfaces. [Figure: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2024
Rhizoctonia Web Blight Development on Container-Grown Azalea in Relation to Time and Environmental Factors
No full text Rhizoctonia web blight, caused by binucleate Rhizoctonia spp., is an annual problem in the southern United States on container-grown azaleas (Rhododendron spp.) that receive daily irrigation. Disease progress was assessed weekly from mid-May to mid-September on nursery-grown plants at three locations in Mississippi and Alabama in 2006, 2007, and 2008. Disease onset, defined as the appearance of blighted leaves at the exterior canopy of at least one plant, occurred on average on 20 July, and calendar date was a more precise predictor of disease onset than several combined time–weather variables. Disease progress curves exhibited weekly fluctuations around a typically exponential increase in the mean number of symptomatic leaves per plant until early to mid-September, after which web blight severity leveled off or declined due to disease-induced leaf dehiscence and the appearance of new, asymptomatic leaves. Based on the relative increase in the log-transformed number of infected leaves per plant, weekly assessment periods were classified as having slow (≤0%), intermediate (>0 to <10%), or rapid (≥10% increase) disease progress. Three-day moving averages (MA) of various weather variables were calculated, and lagged values (by 5 days) of the MA were used in an attempt to predict disease progress as slow, intermediate, or rapid. Of the periods assessed as having slow disease progress in the 2006–2007 data set (model development data), 90.6% (29 of 32) met at least one of the following heuristically derived criteria for the lagged MA: min. temperature < 20.0°C, max. temperature > 35.0°C, avg. vapor pressure deficit < 2.50 hPa, or day of the year > 240 (28 August). One or more of these same criteria were met in 5 of 16 (31.2%) assessment periods with rapid disease progress, indicating that periods with slow versus rapid disease progression could be distinguished reasonably well based on weather. Results were similar for the 2008 validation data. However, weather variables were not useful in separating periods with either slow or rapid disease progress from those having intermediate progress. Instead, weather variables were most useful when used in a negative-prognosis approach to predict disease progression as being “not rapid” (which includes slow and intermediate periods) or “not slow” (including intermediate and rapid periods). The data set was further analyzed using Classification and Regression Tree (CART) analysis to relate weekly disease progress periods to weather variables. The resulting CART model agreed with the heuristic approach in that temperature variables were more prominent than moisture variables in classifying disease progress periods. With both approaches, satisfactory accuracy was accomplished only with negative-prognoses that classified disease progress periods as not rapid or not slow based on temperature and moisture limits. </jats:p
Plant Spacing Effects on Microclimate and Rhizoctonia Web Blight Development in Container-grown Azalea
No full text
Environmental Influences on the Drying Rate of Spray-Applied Disinfestants from Horticultural Production Surfaces
No full textDrying rates of disinfestants commonly applied to horticultural plant production surfaces were evaluated under cool to hot weather and under laboratory conditions to characterize the range of drying times and how this relates to contact times specified on product labels. Drying rates of six disinfestants (isopropyl alcohol [IPA], two quaternary ammonium compounds [QACs], two peroxygen compounds [PXs], and sodium hypochlorite [bleach]) and water were evaluated when applied to six substrate materials (concrete, galvanized metal, polypropylene ground fabric, polyethylene plastic sheet, pressure-treated pine, and twin-wall clear polycarbonate) based on the weather variables of solar radiation, temperature, and relative humidity. Differences were evident at the point of application. Disinfestants with low (IPA, both QACs, and one PX) and high (bleach, one PX, and water) surface tension provided approximately 100 and 60% coverage, respectively, when applied to horizontal, nonporous solid materials. Disinfestants applied to horizontal porous materials (concrete, fabric, and wood) persisted on the surface for a mean of only 9 to 113 s because solutions were actively drawn into the substrates’ internal structure. Disinfestants applied to vertical twin-wall greenhouse material flowed off, while retaining only a maximum beaded wetness coverage of 14%. A Bayesian analysis procedure was used to model drying effects of disinfestants correlated with substrate and weather variables based on posterior marginal and prediction trends. Generally, the fastest drying rate occurred in the first 2.5 min, and approximately 50% of coverage was retained by 5 min. The evaporative process was variable with distinct interactions occurring among the experimental variables. [Figure: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2024
Environmental factors impact temporal <i>Passalora sequoiae</i> conidia counts from Leyland cypress
No full text
Chemical and Hot Water Treatments to Control Rhizoctonia AG P Infesting Stem Cuttings of Azalea
No full text- …
